Pheromones stimulate some olfactory sensory neurons (OSNs) in the main olfactory epithelium (MOE), but the transduction mechanism is poorly understood. In recent work in the Restrepo laboratory we show that signal transduction for pheromones and other biologically relevant odors in the MOE involves the transient receptor potential channel M5 (TRPM5). Interestingly, TRPM5-expressing OSNs project to urine- and pheromone-responsive areas in the ventral olfactory bulb. In addition, we find that TRPM5-positive glomeruli respond to biologically relevant odors. Our data suggest that TRPM5 is involved in pheromone transduction, but the molecular mechanism for this postulated role is unknown. In this FIRCA proposal we propose to test the hypothesis that TRPM5 is involved in pheromone signal transduction in the main olfactory epithelium through electrophysiological and calcium imaging experiments. The proposal is a collaboration between the laboratories of Juan Bacigalupo at the University of Chile and the laboratory of Diego Restrepo at the University of Colorado at Denver and Health Sciences Center. We take advantage of the fact that the expertise of the Bacigalupo laboratory in patch clamp electrophysiology is highly complementary to the expertise of the Restrepo laboratory in calcium imaging and mouse genetics. Public Health Relevance: One of the key aspects of implementing a research program to study the molecular basis of disease in a developing country is ensuring strong basic science research and training. In addition, it is important to link basic science groups with scientists working on the molecular basis and clinical aspects of disease. This basic science proposal contributes significantly to these two important aspects of successful biomedical research. The Department of Biology at the University of Chile is among the premier biology departments in Chile. Graduates from this program contribute substantially to research in the molecular basis of disease and faculty from this department undertake or collaborate in projects on the molecular basis of disease. This project will introduce the Bacigalupo laboratory to the generation and use of gene- targeted mice. It is important to indicate that the generation of gene-targeted mice, an important tool in the understanding of biological function, is only starting to be developed in Chile. The Centro de Estudios Cientificos de Valdivia (CECS, http://www.cecs.cl/web/) has been pioneering this effort, but there is little work on generation of gene-targeted mice elsewhere in the country. The award of this grant would result in training of a talented graduate student in generation of gene-targeted mice. In addition, Dr. Restrepo would give a one week course on the use of gene-targeted mice in the study of neural disease at the University of Chile. Because of the interest of both groups in gene-targeted mice, we expect future interactions between the CECS and the Bacigalupo laboratory. Indeed, there already are close ties between the two groups due to common interests on different aspects of neurobiology. Thus, this FIRCA project would strengthen basic science research and training and therefore will provide a substantial contribution to research capacity building in Chile. Another aspect important for the development of research into disease is the formation of a strong link between basic and clinical research. The qualifying grant of this FIRCA application is an NIMH-funded Conte Center grant focused on the study of schizophrenia (see Specific Aims). The overarching hypothesis is that reduced levels of alfa7 nicotinic acetylcholine receptor in the brains of schizophrenics, caused by polymorphism in the alfa7 receptor promoter, are the cause of certain endophenotypes of this disease. The Conte Center grant spans research ranging from basic to a phase I trial of DMBXA, a partial agonist of the alfa7 receptor. Dr. Restrepo's project studies changes in olfactory ability (an endophenotype in schizophrenia) as well as problems with multimodal interactions that result in decreased attention and decreased performance in goal-oriented tasks in schizophrenics. Gene- targeted mice are used in this research and olfaction is targeted as a sensory system for research because mice use this system to communicate (through pheromones and other volatile chemicals). Research in other Restrepo grants focused on the more basic aspects of olfaction have already resulted in important insights that we have been able to apply to the study of endophenotypes of schizophrenia. From our published work and other preliminary experiments that show that there is no expression of TRPM5 in OSNs until postnatal day 15th we know that TRPM5 is important in mouse chemical communication in the adult. Since chemical communication is key in studying endophenotypes of mouse models of schizophrenia, we expect that the FIRCA grant will also result in generation of information relevant to the qualifying grant. Importantly, Drs. Bacigalupo and Restrepo are also involved in a project that attempts to link basic science research with disease-oriented research in Chile. They are both part of a grant application for a supplement to "Proyecto de Anillos", sent to FONDECYT (Chilean Funding Agency for Science and Technology) the for evaluation with Dr. Adrian Palacios of Valparaiso University as the Program Director. The project is centered on the study of Alzheimer's disease using the Octodon degus, a rodent that presents a senile phenotype with striking parallels to Alzheimer's. A decrease in olfactory ability is a hallmark of Alzheimer's and because the olfactory system is relatively simple in its first processing stages, this system can be used to study the pathology of the disease. We expect that the work in our FIRCA grant application would provide information relevant to the "Proyecto de Anillos". Thus, the FIRCA application would contribute to the link between basic science and clinically oriented research in the US and Chile.